Renal imaging

Question 1

What is a KUB used for?

Answer 1

• Kidney-ureter-bladder (flat plate)
• looking for stones (won’t pick up uric acid stones)
• inexpensive
• scout film for IVP (intravenous pyelogram)
• lower abdominal film so you can check out some abdominal pathology
• downside: can’t pick up masses, gas in bowels may obscure kidney stones

Question 2

When is U/S used? How are kidneys scanned?

Answer 2

• first test done in renal disease - fast and cheap, no contrast
• use in expectant mothers with pain
• Renal mass characterization: cyst (benign) vs solid (malignant most likely), size and position of kidney
• detects obstruction - hydronephrosis
• polycystic kidney disease (structural abnormality)
• chronic renal failure (functional abnormality)
• limited by body habitus
• right kidney scanning: anterior, lateral, and posterior
  liver is acoustic view window, left kidney: requires a posterior approach, through the spleen

Question 3

Sonographic appearance?

Answer 3

• ureters are not normally seen
• renal pelvis is black when visible
• medullary pyramids are hypoechoic
• cortex is mid-gray, less echogenic than liver or spleen
• capsule is smooth and echogenic

Question 4

Changes in degrees of hydronephrosis?

Answer 4

• mild - to moderte calyces are dilated a small amt and in severe: dilated almost throughout the whole kidney

Question 5

When is an IVP (intravenous pyelogram used?

Answer 5

• when there is a suspected obstruction of flow of urine and fxn of kidney (stone, papillary necrosis)
• rapid IV bolus of dye with delayed films - see where contrast stops - at location of stone
• done at intervals: get KUB at 1, 5, 10 and 15 min.
• downside: using IV contrast (can’t use if you have renal disease, allergic to contrast)

Question 6

Use of CT scans?

Answer 6

• eval renal tumors and local spread of renal malignancy
• trauma (extra-peritoneal organ)
• renal colic (helical CT with stone protocol):
  small calculi easily visualized
  collecting system dilation
• now GOLD std for suspected stones
• high resolution CT angiography
• can detect smaller cysts (2-3 mm in size) - US will miss these
• CT urography - can ID urothelial tumors better than IVP (downside: sensitive to contrast)
• don’t ha ve to worry about gas in the colon

Question 7

What component in cysts make them higher risk for cancer?

Answer 7

• complex cysts with calcifications

Question 8

When are MRIs used?

Answer 8

• renal mass characterization:
  usually reserved for pts with CT CIs (contrast)
• great tissue contrast (good for complex masses)
• no ionizing radiation and it is expensive
• invasion from tumors..stages kidney tumors
• THey have MRUs (magnetic renal urography): may be better study to check on anatomical renal abnormalities

Question 9

When are renal arteriographies used? What is it?

Answer 9

• invasive with contrast
• need to know Cr
• can also show you anatomy before transplant
• GOLD std for renal artery stenosis
• doppler U/S, MRA and CTA are used as well but you can stent with the angio

Question 10

When is renal venography indicated?

Answer 10

• useful for dx of renal vein thrombosis

Question 11

When is a retrograde/anterograe pyelography indicated?

Answer 11

• dx urinary tract obstruction or tumors
• injects contrast into the ureter to visualize the ureter and the kidney
• helps with placement of ureteral stents
• used to evaluate trauma
• now we usually do CT or US (better view of kidneys)

Question 12

When is nuclear imaging indicated? Process?

Answer 12

• renal perfusion and fxn (DTPA, mag3: dyes)
• obstruction (lasix renal scan) - common at UPJ
• renovascular HTN
• no side effects to dye
• pt lies still for clear pictures and radioisotope tracer is injected into the vein
• a gamma camera detects the radioactivity and images are projected onto a computer
• can find out what percentage each kidney contributes to the total kidney function

Question 13

What is a voiding cystourethrogram?

Answer 13

• noninvasive
• used to eval the urethra, bladder, ureters, and kidney
• pts bladder is filled with contrast via a catheter and once the bladder is full - inspect for reflux into ureters
• procedure ends with pt voiding
• this is done under fluoroscopy
• good for kids with recurrent UTIs, kidney infections - searching for vesicourectal reflux
• in males: eval for urethral abnormalities: posterior urethral valves (valves block urine output)
• pt voids under fluoro with spot films

Question 14

Best initial imaging test for chronic renal failure?

Answer 14

• U/S of kidneys

Question 15

Someone comes in with flank pain and bloating - initial imaging?

Answer 15

• KUB

Question 16

UA: 6-10 RBCs, what is best initial study prior to sending pt to specialist?

Answer 16

• U/S

Question 17

U/S main uses?

Answer 17

• anatomy

- hydronephrosis

Question 18

CT gold std for?

Answer 18

• renal stones

- dx renal tumors

Question 19

What tests are reliable for dx renal vein thrombosis?

Answer 19

• renal venography, CT, MRI

Question 20

MRA’s role?

Answer 20

• increasing role in suspected renovascular HTN

Question 21

How can VUR and scarring be detected early?

Answer 21

• with radioisotope scanning with DMSA or MAG3 and voiding cystourethrogram

Question 22

Renal arteriography is usefulf for tx and dx?

Answer 22

• tx and dx stenosis and eval for transplant